ECU codes, what to do?
Thread Starter
Senior Member
Joined: May 2004
Posts: 252
ECU codes, what to do?
My CEL has been on for ages (EVAP control system), so I finally got round to resetting it this morning, and it threw out 2 new codes...
04-01 Air intake temp sensor
01-02 Mass air flow sensor...
Now I recently changed the filter on my short-ram to a steel mesh type cone (REworks), and added a heat shield (nothing fancy, $20 job from Advanced Auto parts)...
What do I do about these codes? Do I need to change the sensor? Filter? Remove the heat shield?
I friggin hate being a noob
04-01 Air intake temp sensor
01-02 Mass air flow sensor...
Now I recently changed the filter on my short-ram to a steel mesh type cone (REworks), and added a heat shield (nothing fancy, $20 job from Advanced Auto parts)...
What do I do about these codes? Do I need to change the sensor? Filter? Remove the heat shield?
I friggin hate being a noob
0102
Diagnostic Trouble Code 0102 points to a problem with the Mass Air Flow Sensor. The MAFS is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a thin film that is supplied with electric current from the Engine Control Module. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot wire is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.
This malfunction is detected when an out-of-range voltage is sent to the ECM. That voltage might be too high or too low.
a) An excessively high voltage from the MAFS is sent when the engine is not running.
b) An excessively high voltage from the MAFS is sent under light load driving conditions.
Possible causes include...
- Harness or connectors (the sensor circuit is open or shorted.)
- Faulty MAFS
c) An excessively low voltage from the MAFS is sent when the engine is not running.
d) An excessively low voltage from the MAFS is sent under heavy load driving conditions.
Possible causes include...
- Harness or connectors (the sensor circuit is open or shorted.)
- Intake air leaks
- Faulty MAFS
With DTC 0102 the ECM is supposed to switch into Fail Safe mode and limit engine speed to 2400 rpm.
You might want to clean the MAF sensor element inside the maf with Rubbing Alcahol.
0401
Diagnostic Trouble Code 0401 points to a problem with the Intake Air Temperature Sensor. The IATS is mounted in the engine air intake duct, downstream of the air cleaner filter. It detects intake air temperature and transmits a signal to the Engine Control Module. The sensor uses a thermistor, a resistor with a value which is inversely proportional to temperature. The IATS is not directly used to control the engine. It is used only for diagnostic purposes. Therefore the engine should start and run normally, even with the Malfunction Indicator Light on and DTC 0401 stored.
This malfunction is detected when ...
a) An excessively low or high voltage from the sensor is detected by the ECM.
b) The signal from the IATS is inconsistent with the signal received from the Engine Coolant Temperature Sensor.
Possible causes include ...
- Harness or connectors (The sensor circuit is open or shorted.)
- a faulty Intake Air Temperature Sensor
The IATS resistance values should be ...
- at 14 degrees F, 7.0-11.4 Kohms
- at 68 degrees F, 2.1-2.9 Kohms
- at 176 degrees F, 0.27-0.38 Kohms
For further information about the Intake Air Temperature Sensor please refer to the Chilton repair manual (page 4-16) or the Haynes repair manual (page 6-11).
Make sure both sensors are plugged in correctly, shove the wires into the harness, you might have to redo the ground wire on hte MAF if it is bad.
Diagnostic Trouble Code 0102 points to a problem with the Mass Air Flow Sensor. The MAFS is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a thin film that is supplied with electric current from the Engine Control Module. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot wire is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.
This malfunction is detected when an out-of-range voltage is sent to the ECM. That voltage might be too high or too low.
a) An excessively high voltage from the MAFS is sent when the engine is not running.
b) An excessively high voltage from the MAFS is sent under light load driving conditions.
Possible causes include...
- Harness or connectors (the sensor circuit is open or shorted.)
- Faulty MAFS
c) An excessively low voltage from the MAFS is sent when the engine is not running.
d) An excessively low voltage from the MAFS is sent under heavy load driving conditions.
Possible causes include...
- Harness or connectors (the sensor circuit is open or shorted.)
- Intake air leaks
- Faulty MAFS
With DTC 0102 the ECM is supposed to switch into Fail Safe mode and limit engine speed to 2400 rpm.
You might want to clean the MAF sensor element inside the maf with Rubbing Alcahol.
0401
Diagnostic Trouble Code 0401 points to a problem with the Intake Air Temperature Sensor. The IATS is mounted in the engine air intake duct, downstream of the air cleaner filter. It detects intake air temperature and transmits a signal to the Engine Control Module. The sensor uses a thermistor, a resistor with a value which is inversely proportional to temperature. The IATS is not directly used to control the engine. It is used only for diagnostic purposes. Therefore the engine should start and run normally, even with the Malfunction Indicator Light on and DTC 0401 stored.
This malfunction is detected when ...
a) An excessively low or high voltage from the sensor is detected by the ECM.
b) The signal from the IATS is inconsistent with the signal received from the Engine Coolant Temperature Sensor.
Possible causes include ...
- Harness or connectors (The sensor circuit is open or shorted.)
- a faulty Intake Air Temperature Sensor
The IATS resistance values should be ...
- at 14 degrees F, 7.0-11.4 Kohms
- at 68 degrees F, 2.1-2.9 Kohms
- at 176 degrees F, 0.27-0.38 Kohms
For further information about the Intake Air Temperature Sensor please refer to the Chilton repair manual (page 4-16) or the Haynes repair manual (page 6-11).
Make sure both sensors are plugged in correctly, shove the wires into the harness, you might have to redo the ground wire on hte MAF if it is bad.
Thread Starter
Senior Member
Joined: May 2004
Posts: 252
K, just ran down to the garage to check...
The temp sensor on the snorkel was loose, so I snapped it back in... Reckon I'll be OK? I'm not going to be able to clean the MAF sensor filament until later... Should I worry?
I'm sure I had her running over 2400rpm this morning, so did I get lucky?
Also, would resetting the ECU make a difference? Apart from turning of the CEL of course...
I'm sure I had her running over 2400rpm this morning, so did I get lucky?
Also, would resetting the ECU make a difference? Apart from turning of the CEL of course...
Wont make a difference, aside from eliminatinf the CEL for a bit.
If the MAFS was disconnected you wouldnt be able to go over 2400, or if it had completely failed, so you're alright there.
Should be ok by snapping in your temp sensor.
If the MAFS was disconnected you wouldnt be able to go over 2400, or if it had completely failed, so you're alright there.
Should be ok by snapping in your temp sensor.
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Kyle Lee Cleveland
6th Generation Maxima (2004-2008)
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Sep 28, 2015 09:01 PM